The present invention relates to a process for producing dyestuffs from parts of plants, such parts having been dried.
Many processes of this kind are known. It is common to all such processes that only certain dyestuff plants that are especially suitable can be used for this purpose, such plants being, in particular, dyer's furze, dyer's woad, dyer's esade, indigo, and redwood.
These plants have to be gathered very carefully, in keeping with a strict collection regimen, and only live and healthy specimens or parts thereof may be harvested. After careful drying, that takes place at a maximum temperature of 60.degree. C., the dried plant parts are usually extracted and macerated, the dyestuff then being precipitated and dried. In most cases, the dyestuff has to be ground and mixed after the drying process.
The dyestuffs obtained by using known processes do not, with a few exceptions, such as alizarin and indigo, result in particularly lustrous colours. The dyestuffs so produced are not lasting, and can only be used for waterbased dyes.
The range of applications for dyestuffs produced by the known processes is especially restricted in that the colours are not, or are only slightly, fade-resistant. Because these production methods are very involved and time-consuming, starting with the collection regimen, the dyestuffs that are produced are very costly; the process are scarcely suitable for industrial applications.
The dyestuffs produced from parts of plants by the known processes are of limited use since they are not suitable for use on surfaces that are exposed to weathering, and also because they do not adhere to every base. This latter fact is also caused by the fact that they are not miscible with basic materials, and for this reason cannot be mixed with lime and other roughcast materials.
An object of the present invention is to provide a process of the type described in the introduction hereto, by means of which any, particularly lustrous, colours can be produced simply from parts of plants, without restriction to specific dyestuff plants, said colours being miscible with other colours, fade-resistant, and of extended durability.